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KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

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APPENDIX C<br />

13. DATA ASSESSMENT<br />

The goal of the program is to provide analytical data of consistent and known quality for determining the<br />

nature and extent of contamination, assessing risks, instituting corrective actions, and/or identifying and<br />

mitigating threats to public health and the environment. Protocols and methodologies are therefore<br />

designed to provide data of known quality in strict accordance with QA procedures and C-O-C<br />

requirements.<br />

2.39 Formulas<br />

13.1.1 Precision<br />

Multiple aliquots of the samples are spiked and each aliquot is treated exactly the same throughout the<br />

analytical method. Spikes are added at approximately 10 times the method detection limit. The percent<br />

difference between the values of the duplicates, as calculated below, is taken as a measure of the<br />

precision of the analytical method.<br />

%RPD =<br />

where: RPD = Relative percent difference<br />

D1 = First sample value<br />

D2 = Second sample value (duplicate)<br />

13.1.2 Accuracy<br />

2 ( D1- D2 )<br />

x 100<br />

( D1+ D2 )<br />

A control standard is prepared by adding a known amount of pure compound to a blank matrix (before<br />

any extraction is performed). A standard reference material may also be used as both the matrix (i.e.,<br />

reagent grade silica sand) and as the added compound. These samples measure the accuracy of analytical<br />

operations in a standard matrix.<br />

Accuracy as percent recovery (P) is calculated as:<br />

ExperimentalValue<br />

P =<br />

TrueValue<br />

x 100%<br />

A sample spike is prepared by adding a known amount of a pure compound to the environmental sample<br />

before any extraction is performed. The compound is the same or similar (as in isotopically labeled<br />

compounds) as that being assayed in the environmental sample. These spikes simulate the background<br />

and interferences found in the actual samples, and calculated percent recovery of the spike is taken as a<br />

measure of the accuracy of the total analytical method. It is calculated as follows:<br />

P =<br />

100(OH - X)<br />

T<br />

where: P = Percent recovery<br />

OH = Measured analyte concentration<br />

X = Measured analyte concentration in the sample before the spike is added<br />

T = Concentration of spike<br />

Kirtland AFB<br />

Quality Assurance Project Plan C-55 April 2004

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